GPR52 agonists attenuate ropinirole-induced preference for uncertain outcomes

Dopamine D_2/3 receptor agonists are less likely to trigger dyskinesias than L-dopa while still offering relief from the motor symptoms of Parkinson's disease (PD). However, these drugs can cause serious impulse control problems and gambling disorders. Adjunctive therapies capable of blocking these side effects without impacting the antiparkinsonian effect would be clinically useful. G-protein-coupled receptor 52 (GPR52) is an orphan Gs-protein-coupled receptor that is coexpressed with striatal D₂ receptors. Activating GPR52 attenuates behaviors associated with increased striatal dopamine release without altering basal function. Iatrogenic gambling disorder may be mediated, at least partly, by striatal dopamine signaling. We therefore investigated whether 2 potent small-molecule GPR52 agonists (BD442618, BD502657) could block the increase in preference for uncertain outcomes caused by acute d-amphetamine and chronic ropinirole, without altering baseline choice patterns. In the rat betting task (rBT), subjects choose between a guaranteed reward (the "wager") versus the 50:50 chance of double the wager or nothing. Although wager size varies across trial blocks, both options are constantly matched for expected value. The effects of BD442618 on the rBT were acutely assessed alone or in combination with d-amphetamine and subsequently in combination with chronic ropinirole. The latter experiment was then repeated with BD502657. BD442618 did not alter baseline decision making but attenuated the increase in preference for uncertainty caused by both acute amphetamine and chronic ropinirole administration. Similarly, BD502657 abrogated chronic ropinirole's effects. These data provide the first evidence that GPR52 agonists may be useful in treating iatrogenic gambling disorder or other conditions hallmarked by hyperdopaminergic states. (PsycInfo Database Record (c) 2021 APA, all rights reserved).